Nuytsia WESTERN AUSTRALIA's JOURNAL of SYSTEMATIC BOTANY ISSN 0085–4417
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Nuytsia WESTERN AUSTRALIA'S JOURNAL OF SYSTEMATIC BOTANY ISSN 0085–4417 B.L. Rye. Reinstatement of the Western Australian genus Oxymyrrhine (Myrtaceae: Chamelaucieae) with three new species Nuytsia 19(1): 149–165 (2009) All enquiries and manuscripts should be directed to: The Managing Editor – NUYTSIA Western Australian Herbarium Telephone: +61 8 9334 0500 Dept of Environment and Conservation Facsimile: +61 8 9334 0515 Locked Bag 104 Bentley Delivery Centre Email: [email protected] Western Australia 6983 Web: science.dec.wa.gov.au/nuytsia AUSTRALIA All material in this journal is copyright and may not be reproduced except with the written permission of the publishers. © Copyright Department of Environment and Conservation B.L.Nuytsia Rye, 19(1): Reinstatement 149–165 (2009) of the Western Australian genus Oxymyrrhine 149 Reinstatement of the Western Australian genus Oxymyrrhine (Myrtaceae: Chamelaucieae) with three new species Barbara L. Rye Western Australian Herbarium, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, Western Australia 6983 Abstract B.L. Rye. Reinstatement of the Western Australian genus Oxymyrrhine (Myrtaceae: Chamelaucieae) with three new species. Nuytsia 19(1): 149–165 (2009). The south-western Australian genus Oxymyrrhine Schauer is reinstated and the type species, previously known as Baeckea polyandra F.Muell., is restored to its earlier name of O. gracilis Schauer. A lectotype is selected for B. polyandra and three new species, Oxymyrrhine cordata Rye & Trudgen, O. coronata Rye & Trudgen and O. plicata Rye & Trudgen, are described. These four species make up a group described here as Oxymyrrhine s. str. and are distinguished from other members of Oxymyrrhine s. lat. and from all other genera of tribe Chamelaucieae by the broad cavity in the summit of their fruit. Oxymyrrhine s. lat. includes a particularly difficult species complex, which will be revised at a later time. Introduction Oxymyrrhine Schauer is a south-western Australian genus belonging to tribe Chamelaucieae s. lat. of the Myrtaceae. The genus was named by Schauer (1843) based on the single species O. gracilis, which Mueller (1864) later redescribed as Baeckea polyandra. Schauer appears to have relied on the numerous stamens and the anther type to defineOxymyrrhine , while Mueller was the first to describe fruiting material, recording that the capsule was enclosed (not protruding) and the seeds were small, brown and trigonous-semicircular. In Flora Australiensis, Bentham (1867) treated the genus as a section of his very broadly defined genus Baeckea L. Since the epithet of the type species of Oxymyrrhine had already been used in Baeckea s. lat., it was necessary for the later-published name Baeckea polyandra to be accepted for the species. Bentham listed five south-western Australian species in Baeckea sect. Oxymyrrhine, adding Baeckea crispiflora (F.Muell.) F.Muell., B. corynophylla (F.Muell.) F.Muell. and two species closely allied to the latter. Niedenzu (1893) recognised six species within Oxymyrrhine, which he maintained as a section but included within his new group Baeckea subgenus Hysterobaeckea Nied. All members of the Hysterobaeckea group have a derived anther type with the connective gland united to other parts of the stamen. DNA samples collected as part of the current study included the type species of Oxymyrrhine and a Darling Range species that was described as Baeckea sp. A in Flora of the Perth Region (Rye 1987). In unpublished analyses based on several chloroplast regions (the matK gene, the 5’ trnK intron, part of 150 Nuytsia Vol. 19(1) (2009) the ndhF gene and the atpB-rbcL intergenic spacer), these two species formed a well-supported clade (Peter Wilson pers. comm.). When the ETS nuclear region was examined, the two species remained together and formed part of a much larger clade comprising taxa with the Hysterobaeckea anther type, including members of the Baeckea crispifloracomplex. The unpublished data suggest that additional genera including Oxymyrrhine should be recognised, but currently do not provide any strong support for the inclusion of the B. crispiflora complex within Oxymyrrhine. Oxymyrrhine is reinstated in the current paper, and three new closely related species that were unknown to the nineteenth century botanists are named. These four species are referred to here as Oxymyrrhine s. str. Revisionary studies of other species groups that were included in section Oxymyrrhine by Bentham (1867) are not far enough advanced to estimate how many species should be recognised. The Baeckea crispiflora complex is particularly problematic, and the name B. crispiflora may have to be discarded as three earlier species epithets (leptophylla, parvifolia and serpyllifolia) published by Turczaninow (1852) apply to members of the complex. Methods Descriptions are based on well-pressed dried material, using similar methods to those described in other recent papers on Western Australian Chamelaucieae such as Rye (2002). Holotypes for the new species have been lodged at PERTH. For those species with conservation priority, precise localities have been withheld for all specimens cited. The distribution map was compiled using DIVA-GIS freeware Version 5.2.0.2. Reinstatement of Oxymyrrhine It has long been acknowledged that one or more genera with the Hysterobaeckea anther type should be reinstated (see Johnson & Briggs 1984, Rye 1987 and Lam et al. 2002), and the eastern Australian species of the Hysterobaeckea have already been removed from Baeckea (Bean 1997, Wilson et al. 2007). Despite this, not even the oldest available name, Babingtonia Lindl. (Lindley 1842), has been used since Bentham’s time for members of the group in Western Australia. Shortly after Babingtonia was established, Schauer (1843) described three more genera belonging to the Hysterobaeckea group: Oxymyrrhine, Harmogia Schauer and Tetrapora Schauer. Since then, a number of additional generic names have been published, those currently in use being Balaustion Hook., Kardomia Peter G.Wilson, Malleostemon J.W.Green, Sannantha Peter G.Wilson and Scholtzia Schauer, and an additional genus, Cheyniana Rye, is published in the accompanying paper (Rye 2009). Comparison with Babingtonia, Harmogia and Tetrapora For Oxymyrrhine to be reinstated it must first be established that the type species of Babingtonia and Oxymyrrhine are not congeneric, since the earlier name Babingtonia has priority. A paper (jointly authored with M.E. Trudgen) reinstating Babingtonia as a Western Australian endemic genus is currently in preparation. Babingtonia was previously treated by Bean (1997) as the sole generic name for eastern Australian species of the Hysterobaeckea group; however this very broad definition of the genus has not been supported by molecular data (Lam et al. 2002, Wilson et al . 2004) and most of the eastern species have now been placed in two new genera (Wilson et al. 2007). The type species of Babingtonia, B. camphorosmae Lindl., and its closest relatives occur in the south-west of B.L. Rye, Reinstatement of the Western Australian genus Oxymyrrhine 151 Western Australia and are readily distinguished from Oxymyrrhine by their more compressed stamen filaments, by their helmet-like anthers, which vary from compressed-obovoid to deeply divided into two divergent lobes and which often have two longitudinal lateral grooves, and by their longer and much thicker seeds with a more flattened base and more angled summit. One of the two genera named concurrently with Oxymyrrhine, the monotypic eastern Australian genus Harmogia, has recently been reinstated (Wilson et al. 2007). Cladistic data presented in that paper suggest that Harmogia is most closely related to the eastern Australian taxa now placed in the new genus Sannantha. Bentham (1867) placed the members of these genera in Baeckea sect. Harmogia (Schauer) Benth. & Hook.f. Harmogia differs from Oxymyrrhine in having its seeds flattened at the base rather than curved at both ends like the segments of an orange as in Oxymyrrhine and has a testa of flat to concave cells which are much larger than the colliculate cells on seeds ofOxymyrrhine . It also shows subtle differences in its anther morphology, with its connective gland extending dorsally not only well beyond the anther loculi but also down beyond the top of the free part of the filament. A more obvious difference is its tendency to have very dense clusters of leaves on its lateral branchlets. Unlike Harmogia, the other concurrently named genus, Tetrapora, has not yet been reinstated and its delimitation and morphology have not been fully determined. Bentham (1867) placed the members of the genera Tetrapora and Babingtonia in Baeckea sect. Babingtonia (Lindl.) Benth. & Hook.f., and molecular data (Wilson et al . 2004) place them in the same clade, together with species of Malleostemon and Scholtzia. Tetrapora can be distinguished from Oxymyrrhine s. str. by its tendency to have multiple flowers per axil, by its less numerous stamens (5 to 14 per flower), which are all antisepalous, and by its more tubular depression in the ovary summit. Establishing character differences between Tetrapora and Oxymyrrhine s. lat. is deferred until both groups have been studied further. Delimitation of Oxymyrrhine The type species of Oxymyrrhine and its three closest relatives, i.e. the members of the typical group referred to here as Oxymyrrhine s. str., are characterised by a deep and distally-expanded depression in the summit of the mature dried fruit, which remains fully or almost fully inferior. This broad cavity is also evident in the ovary summit of flowers in all dried material, exposing the part of the style that is below the summit of the ovary. Other genera of tribe Chamelaucieae either lack a deep cavity or have a tubular one closely surrounding the lower part of the style. In the typical group of Oxymyrrhine the base of the depression is sometimes contracted into a very short tubular portion closely surrounding only the extreme base of the style. At maturity, the style may either remain included within the cavity or become exserted from it. All of the species that were added to the Oxymyrrhine group by Bentham, such as the B.